1. Field of the Invention
The present invention is directed in general to the field of information of electronic circuitry. In particular, the present invention relates to systems and methods for providing exponential charge pumps.
2. Description of the Related Art
Charge pumps are commonly used in integrated circuits to increase power supply voltages for specific applications, such as the operation of memory arrays. One common type of charge pump is the “arithmetic” charge pump comprising multiple pump stages, with the final output voltage of the charge pump being a linear multiple of the input voltage. As power supply values decrease and pump output value requirements increase, the number of stages required by an arithmetic pump becomes prohibitive. For example, to achieve 14.5V from a 1.7V supply currently requires eight stages.
Another charge pump configuration is an “exponential” charge pump comprising multiple stages with the increase in voltage being exponentially proportional to the voltage increase of each stage with the exponent being equal to the number of stages. For example, an exponential comprising three stages with each stage doubling the voltage would produce an output voltage equal to (input voltage)*23, or eight times the input voltage.
In many small non-volatile memory arrays, charge pumps consume a significant portion of the die area. For example, current designs for exponential charge pumps require level shifters and smoothing capacitors that require a large amount of die surface area and also consume a disproportionately high amount of power. It would be desirable to provide a charge that reduces the number of stages and that minimizes the use of level shifters and related circuit components.
It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the drawings have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for purposes of promoting and improving clarity and understanding. Further, where considered appropriate, reference numerals have been repeated among the drawings to represent corresponding or analogous elements.